1. Field of the Invention
The present invention relates to illuminating method and apparatus in which, when the outer appearance of a surface having a curved portion is inspected, the surface to be inspected is illuminated.
2. Description of the Related Art
Conventionally, as an apparatus in which, when the outer appearance of a curved surface, particularly, an inner peripheral surface of a concave member is inspected, the curved surface to be inspected is illuminated without causing local reflection unevenness, a diffuser such as a light diffusion filter or a light diffusion plate is provided for a light source. The use of the diffuser allows light to be evenly spread all over a region to be illuminated.
Alternatively, a fluorescent light in which a light source itself emits diffused light may be selected. The fluorescent light includes an inner peripheral surface of a cylinder-shaped fluorescent pipe which is coated with a light diffusion material. Therefore, the fluorescent light itself has the same effect as that of the aforementioned diffuser.
Further, it is also considered that uniformity of light from a light source is realized by providing an arrangement of a plurality of point light sources each having a small quantity of light, for example, light emitting diodes (LED). Although each having a small quantity of light, LED allows diffusion of light over a wide region and can be regarded as a surface light source.
According to the light source having the aforementioned structure, a required sufficient quantity of light can be obtained when the outer appearance of an inner peripheral surface of a concave member is visually inspected. An inner peripheral surface of a tire is an example of the concave member.
However, the inner peripheral surface of the tire applied as the concave member is bent in a three-dimensional manner. From the standpoint of a tire structure, an opening is formed at an inner side of a donut-shaped structure and irregularities are provided on a concave inner peripheral surface. Accordingly, in the light source having the aforementioned structure, light is difficult to reach up to a rear side of a convex portion, and even if light is uniformly emitted from a light source, the quantity of light received by an inner surface which is practically irradiated with light becomes ununiform. The quantity of light received is the quantity of reflected light, alternatively. As a result, outer appearance inspection cannot properly be carried out.
In view of the aforementioned circumstances, an object of the present invention is to provide an illuminating apparatus in which when the outer appearance of a surface having a curved portion is inspected, light can be evenly illuminated on the surface to be inspected and outer appearance inspection can be properly carried out.
A first aspect of the present invention is an illuminating apparatus in which when an outer appearance of a surface having a curved surface is inspected, the surface to be inspected is illuminated, comprising: a density detecting device which is capable of detecting a density of at least a region whose outer appearance is to be inspected; a light source unit provided with a predetermined number of light emitting portions which emit light for illuminating the region whose outer appearance is to be inspected, and also provided with a base plate having the predetermined number of light emitting portions and made of a flexible material; a locating device for locating the light source unit along a curvature of the surface at a predetermined space to a surface of the region whose outer appearance is to be inspected; and an emitted-light-quantity control device for controlling a quantity of light from the light emitting portions based on a result of detection by the density detecting device.
The illuminating apparatus includes the light source units which are provided by the locating device along the surface of a region whose outer appearance is to be inspected. As a result, the light source units are substantially disposed at a predetermined space to the surface.
However, in a case in which the surface is formed so as to have irregularities, light does not reach up to a concave portion interposed between convex portions. Even if the quantity of light from light emitting portions is made uniform, reflected light from the surface becomes ununiform. As a result, outer appearance inspection is impeded.
Accordingly, in the present invention, the density of the region whose outer appearance is to be inspected is detected by the density detecting device, and based on the result of detection, the quantity of light from the light emitting portions is increased or decreased. In a case in which a plurality of light source units are used, the quantity of light may be increased or decreased for each light source unit.
In other words, the quantity of light from a light source unit corresponding to a region to which light does not reach is increased, and the quantity of light from a light source unit corresponding to a region in which the quantity of reflected light locally increases due to irregular reflection or the like is decreased. As a result, the quantity of light reflected from the region to be visually inspected can be made substantially uniform, and outer appearance inspection for checking whether there is a flaw or the like can be properly carried out.
In the present invention, preferably, the emitted-light-quantity control device is formed by: a density distribution preparing device for, based on a detection result of density from the density detecting device, preparing a density distribution of the region whose outer appearance is to be inspected; and an emitted-light-quantity increase/decrease device for increasing or decreasing a quantity of light emitted from the light emitting portions so that the density distribution prepared by the density distribution preparing device is made uniform.
The present invention provides light-quantity control of the light emitting portions. That is, a density distribution of the region whose outer appearance is to be inspected is prepared based on a result of detection by the density detecting device, and the quantity of light emitted from the light emitting portions is increased or decreased so that the prepared density distribution becomes uniform. The density distribution is based on the quantity of reflected light at the time outer appearance inspection is carried out. Therefore, a condition on which an outer appearance inspection is visually carried out by an operator can be made proper.
In the present invention, more preferably, a reference density value included in the uniform density distribution is a previously-set density value.
According to the present invention, a reference value is required in the uniform density distribution. More preferably, it suffices that, due to a reference density value being previously set, the quantities of light from all light emitting portions may be increased or decreased so as to become the previously-set density value.
In the present invention, still more preferably, a reference density value included in the uniform density distribution is an average density value of the region whose outer appearance is to be inspected.
According to the present invention, the reference density value included in the uniform density distribution is set as an average density value of a detected density distribution. Therefore, it is not necessary to previously set a reference density.
In the aforementioned aspect of the present invention, further preferably, the surface of the region whose outer appearance is to be inspected is an inner peripheral surface of a concave member.
When the surface of the region whose outer appearance is to be inspected is an inner peripheral surface of a concave member, even if the quantity of emitted light is fixed, a uniform quantity of reflected light is difficult to be obtained. In this case, the effect of the present invention can sufficiently be exhibited.
In the aforementioned aspect of the present invention, still further preferably, the surface of the region whose outer appearance is to be inspected is an inner peripheral surface of a tire.
Particularly in a tire structure, an opening is provided at an inner side of a donut-shaped configuration. Therefore, the quantities of light from the light source units are not difficult to reach to the inner peripheral surface, and are apt to become ununiform. Due to the present invention being applied to the outer appearance inspection for the inner peripheral surface of the tire, there is no possibility that an operator may fail to notice a flaw or the like, or fail to recognize a shadow as a flaw. As a result, inspection efficiency can be improved.